Brake system for vehicle

Abstract

A brake system for a vehicle, may include a brake input device to apply a brake input of a driver; a brake actuator generating braking hydraulic pressure; wheel cylinders generating braking force for each vehicle wheel by the braking hydraulic pressure generated by the brake actuator; and a hydraulic pressure supply line connecting the brake actuator and the wheel cylinders, wherein the brake actuator includes a main pump device by which braking force is applied, and a sub control device configured for adjusting the braking force applied by the main pump device.

What is claimed is: 
     
       1. A brake system for a vehicle, the brake system comprising:
 a brake input device configured to apply a brake input of a driver; 
 a brake actuator configured for generating braking hydraulic pressure; 
 wheel cylinders configured for generating braking force for each vehicle wheel by the braking hydraulic pressure generated by the brake actuator; and 
 a hydraulic pressure supply line connecting the brake actuator and the wheel cylinders, 
 wherein the brake actuator includes a main pump device by which braking force is applied, and a sub control device configured for adjusting the braking force applied by the main pump device, and 
 wherein the sub control unit includes:
 a second housing having an internal space therein; 
 a sub piston which is disposed in the second housing to be movable forwards and backwards therein; and 
 a sub motor configured for providing driving power for moving the sub piston forward or backward thereof. 
 
 
     
     
       2. The brake system according to  claim 1 , wherein the main pump device includes:
 a two-stage structured main piston having a small diameter portion and a large diameter portion; 
 a first housing having a two-stage structured internal space corresponding to a shape of the main piston; and 
 a main motor configured for providing driving power for moving the main piston forward or backward thereof. 
 
     
     
       3. The brake system according to  claim 2 , wherein in the first housing a first chamber being pressed by the small diameter portion and a second chamber being pressed by the large diameter portion are formed. 
     
     
       4. The brake system according to  claim 2 , wherein the main piston has a hollow portion formed at one end portion thereof and in the hollow portion a spring member is disposed. 
     
     
       5. The brake system according to  claim 2 , wherein the main pump device further includes a first transmission member disposed between the main piston and the main motor, and the first transmission member is configured to convert rotational force of the main motor into straight conveying force. 
     
     
       6. The brake system according to  claim 5 , wherein the first transmission member includes a screw and a nut. 
     
     
       7. The brake system according to  claim 1 , wherein in the second housing a third chamber and a fourth chamber are formed and are defined by the sub piston, wherein the third chamber is connected to the first chamber and the fourth chamber is connected to the second chamber. 
     
     
       8. The brake system according to  claim 7 , wherein the first housing and the second housing are integrally formed and have a first flow path for connecting the first chamber and the third chamber and a second flow path for connecting the second chamber and the fourth chamber therein. 
     
     
       9. The brake system according to  claim 1 , wherein the sub control device further includes a second transmission member disposed between the sub piston and the sub motor, and the second transmission member is configured to convert rotational force of the main motor into straight conveying force. 
     
     
       10. The brake system according to  claim 9 , wherein the second transmission member includes a screw and a nut. 
     
     
       11. The brake system according to  claim 3 , wherein the small diameter portion of the main piston has at least one through hole, which is configured to selectively connect the first chamber and a reservoir hydraulic line extending from an oil reservoir, formed therein. 
     
     
       12. The brake system according to  claim 5 , wherein the main piston and the first transmission member are configured to be separable from each other, wherein, when the main motor breaks down, the main piston and the first transmission member are separated by a pedal effort provided by a driver to generate braking hydraulic pressure. 
     
     
       13. The brake system according to  claim 12 , wherein the main pump device is connected to a master cylinder through a pedal hydraulic line, and wherein the pedal hydraulic line has a normally open valve disposed therein. 
     
     
       14. The brake system according to  claim 7 , wherein the brake actuator is connected to a front wheel or a rear wheel; the third chamber is connected to one of left and right wheel cylinders of the vehicle wheels connected through the hydraulic pressure supply line; and the fourth chamber is connected to the other wheel cylinder through the hydraulic pressure supply line. 
     
     
       15. The brake system according to  claim 7 , further including:
 a controller configured for controlling the brake actuator. 
 
     
     
       16. The brake system according to  claim 15 , wherein the controller is configured to control the sub motor to adjust a position of the sub piston, and as a result, pressure inside the third chamber or the fourth chamber is increased to produce a difference between left and right braking forces. 
     
     
       17. The brake system according to  claim 15 , wherein the controller is configured to produce emergency braking force when the main pump device breaks down by controlling the sub motor to adjust a position of the sub piston and thus to increase pressure in the third chamber or the fourth chamber. 
     
     
       18. The brake system according to  claim 3 , wherein a predetermined area of the small diameter portion in the first chamber is equal to a predetermined area of the large diameter portion in the second chamber. 
     
     
       19. The brake system according to  claim 3 , wherein sealing members are configured to be inserted into the first chamber and the second chamber between an interior of the housing and the main piston, respectively.